The present invention generally relates to a novel system and a novel method for aligning multiple parts of a larger piece of machinery for subsequent assembly into the larger piece, such as a piece of construction equipment. The invention more specifically relates to a novel system for and a novel method of aligning an upper works and a lower works of a piece of construction equipment, such as joining or redecking the upper works of a lift crane with its lower works.
Large pieces of machinery, such as cranes, excavators and other construction equipment, are often very expensive, sometimes costing on the order of hundreds of thousands of dollars. For many contractors, it is not economically feasible to own more than a few pieces of such machinery. Therefore, it is desirable to be able to transport this equipment from one job site to another in order to limit the number thereof which must be kept on hand in order to effectively compete in the construction business.
Because cranes and the like are often very large and heavy, possibly on the order of hundreds of tons, they can be quite difficult to transport. Certain weight restrictions on roads may prohibit contractors from moving their heavy equipment from one job site to another along the shortest or most convenient route. The contractors may be forced to take long, meandering paths during transport of the equipment. Because of the increased length of many of these paths, the travel time may be correspondingly increased, which can lead to lost revenues to the contractor due to the higher transportation costs, e.g. fuel, man power, and the like, and down time of the equipment during transport.
In an effort to facilitate this transport, construction equipment has been developed which comprises a plurality of smaller, lighter parts which can be repeatedly disassembled and reassembled. One example of such construction equipment is a self-assembling crane which generally comprises an upper works and a lower works that are releasable connectable. To transport this crane from one job site to another, the upper works is disassembled or undecked from the lower works. In some instances, undecking can be accomplished by a plurality of jacks which can raise the upper works off of the lower works. Once undecked, the upper works and the lower works can be loaded onto separate transport trailers and moved individually to the next job site. This may allow the contractor to use the shortest path between the two sites, thereby reducing transport and down time, to move the upper and lower works. Once the two works arrive at the next job site, they can be assembled or redecked to form the crane.
The methods of redecking can be rather complex. The upper works may be lifted by the jacks a sufficient distance to allow the lower works to be positioned underneath the upper works. Then, the upper and lower works must be aligned with respect to each other within acceptable tolerances for facilitating their assembly. This alignment can be difficult, especially upon consideration that both the upper works and the lower works may be quite heavy and burley, and that the tolerances may be rather small. Alignment may also be complicated by the possibly uneven terrain of the construction site. The alignment of the upper works with the lower works may become tedious, and considerable time and man power may have to be spent to properly align the works. The time and labor spent in aligning and subsequently redecking the upper works with the lower works may reduce the revenues saved by undecking the works in the first place.
One method of solving problems associated with the alignment of a crane upper works with a corresponding lower works is disclosed in U.S. Pat. No. 4,601,401. That patent discloses a redecking alignment system utilizing a number of interengagable centering pins and sockets. The upper works including the pins is placed upon the lower works which includes the sockets. The sockets are tapered, and a lubricous substance is provided adjacent the sockets to encourage the pins to slide into the sockets. As the centering pins slide into the sockets, the crane upper works moves into alignment with the lower works, thereby facilitating redecking. Once the pins are in the sockets, the pins must be removed to finish redecking the upper works with the lower works.
While this method may provide some advantages over other alignment systems and methods, this method possesses some drawbacks which may make it unattractive to some, and may render its performance suboptimal. Thus, a crane having this alignment system may not be desirable to some contractors.
For instance, this method requires the use of a float means under each of the jacks which raise and lower the upper works during alignment and redecking. The float means permits lateral shifting of the upper works relative to the lower works to facilitate full seating of the centering pins in the sockets as the upper works is lowered with respect to the lower works. This float means is expensive, creates an inherent instability in the structure during redecking, especially on uneven terrain, and adds additional elements which must be carefully monitored during alignment and redecking in order to insure proper alignment of the upper works with the lower works. Thus, the presence of the float means may further complicate the redecking procedure, and may increase the mount of time and labor required to transport and redeck the upper and the lower works. Once the works are aligned, the upper works must be raised in order to retract the centering pins, which adds yet a further step to the redecking procedure.
Another alignment system is disclosed in co-pending U.S. patent application Ser. No. 07/762,765, filed on Sep. 21, 1991. The disclosure of that application is incorporated herein in its entirety by reference. This system has many advantages, but is not constructed for use with truck mounted lift cranes, which have increased weight with respect to the lower works and asymmetrical axle placement. However, it is envisioned that this alignment system may be used with relatively small truck cranes.
As can be appreciated from the foregoing discussion, it is desirable to develop a novel apparatus and method for redecking an upper works with a lower works which is not subject to some, if not all of the limitations which effect the apparatuses and methods of the prior art. The present invention is intended to provide such a novel apparatus and method.